1. Field
Example embodiments may relate to phase-change material layers, methods of forming a phase-change material layer, and/or methods of manufacturing a memory device including a phase-change material layer. For example, example embodiments may relate a phase-change material layer that may be formed by using a plasma at a relatively lower temperature, a method using a plasma at a relatively lower temperature, and/or a method of manufacturing a phase-change memory device including a phase-change material layer using a plasma.
2. Description of the Related Art
Semiconductor memory devices may be generally divided into volatile semiconductor memory devices such as dynamic random access memory (DRAM) devices or static random access memory (SRAM) devices, and non-volatile semiconductor memory devices such as flash memory devices or electrically erasable programmable read only memory (EEPROM) devices. The volatile semiconductor memory device may lose stored data if power is discontinued. The non-volatile semiconductor memory device may retain stored data even though power is discontinued.
Among related art non-volatile semiconductor memory devices, flash memory devices have been used in various electronic apparatuses such as digital cameras, cellular phones, MP3 players, and/or similar devices. Programming and/or reading may require relatively longer amounts of time for flash memory devices. Semiconductor memory device such as a magnetic random access memory (MRAM) device, a ferroelectric random access memory (FRAM) device, and/or a phase-change random access memory (PRAM) device may require smaller amounts of time to program and/or read.
The phase-change memory device may store information by exploiting resistance differences between amorphous phases and crystalline phases of a phase-change material layer including a chalcogenide compound such as germanium-antimony-tellurium (GST) or the like. The PRAM device may store data as “0” and “1” using a reversible phase transition of the phase-change material layer. An amorphous phase of the phase-change material layer may have a larger resistance than a crystalline phase of the phase-change material layer. In the PRAM device, a transistor formed on a substrate may provide a phase-change material layer with a reset current (Ireset) for changing the phase of the phase-change material layer from a crystalline state into an amorphous state. The transistor may also supply the phase-change material layer with a set current (Iset) for changing the phase of the phase-change material layer from the amorphous state into the crystalline state. Related art PRAM devices and related art methods of manufacturing a PRAM device may include forming a phase-change material layer of GST through a sputtering process and/or an evaporation process.
In related art method of manufacturing the PRAM device, the phase-change material layer including GST may be formed by a physical vapor deposition (PVD) process such as a sputtering process and/or an evaporation process, but phase-change material formation rate in these processes may not be properly controlled. Phase-change material layers may not have a dense crystalline structure and/or not have a face centered cubic (FCC) crystalline structure, such an FCC structure providing better electrical characteristics. Further, concentration ratios among germanium, antimony, and/or tellurium may not be adequately controlled if the phase-change material layer is formed by the PVD process. The phase-change material layers formed by the PVD process may not have adequate phase transition if a set current is applied to the phase-change material layer. Phase-change material formation rate may be relatively slower such that manufacturing cost and time may be higher.